Value tokens, such as casino gaming chips, have the attributes of currency and, accordingly, significant steps are taken to track the location and value of such value tokens as well as to prevent their counterfeiting and theft. For example, gaming chips with transponders formed therein are described in U.S. Pat. Nos. 5,166,502; 5,895,321; 6,264,109; 6,296,190; 6,581,747; 7,866,563; 7,918,455; 7,926,725; 7,931,204; and 7,942,334. As described in these applications, the transponders may be molded within plastic injection molded gaming chips and detected using conventional RFID detectors or other readers. The transponders typically transmit unique identification information and value information to such readers for detection and verification. However, it is generally desired that such gaming chips have heavier weights for easier manipulation by the gaming customers and dealers. Accordingly, many gaming chips are formed with metal (e.g., brass) slugs within the plastic outer coverings to add the desired weight.
For example, conventional gaming chips are formed by overmolding an injection molded plastic rim around a brass coin or other metal slug. The metal slug is selected to account for at least 50% of the weight (e.g. 12-13 grams) of the gaming chip, while the plastic accounts for the other 50% of the weight. A label or decal is then added over the visible surface of the gaming chip. Unfortunately, such slugs interfere with the operation of high frequency RFID transponders by forming a high frequency shield that detunes the RFID transponders, typically preventing such gaming chips from including RFID transponders.
One way to address this problem is to provide the RFID microchip and RFID antenna on top of the gaming chip. For example, the antenna may be printed onto the chip using, e.g. conducting ink, at a position on top of the metal slug. The RFID microchip and printed antenna is then covered by a decal so that it is not apparent to the user. Alternatively, an RFID inlay is provided between the metal inlay and the decal for accepting the RFID microchip. However, such designs have numerous problems including, for example, rupture of electrical contacts by peeling off, destruction of the RFID microchip in the event of shock, as when two chips are “banged” against each other or when one gaming chip is hit with the edge of another gaming chip, deactivation of the RFID microchip by scraping with a nail, removal of the RFID microchip, and the like. Also, the metal slug still shields and detunes the RFID signal and may not work at all unless the density of the metal is significantly reduced.
Thus, while it remains desirable to design gaming chips and other value tokens with the desirable weights afforded by metal slugs, the use of the metal slugs has heretofore dictated designs that render the transponders either ineffective or subject to damage. It is desired to design value tokens, including gaming chips, that enable use of RFID microchips without the aforementioned shortcomings in prior art gaming chip designs.
Those skilled in the art will further appreciate that counterfeiting and theft remain a problem with value tokens. Numerous security features such as watermarks, special fluorescent inks, security pigments, holograms, encryption of the values stored in the RFID microchips, and the like are commonly used to make counterfeiting more difficult. Also, electromagnetic (EM) materials such as, but not limited to, coils or metallic detectable foils, are conventionally applied to gaming chips to help deter employees from unauthorized attempts to remove the value tokens from the casino floor. Portable handheld electromagnetic detection devices or gates at the exits may be used to detect such devices by detecting resonation of the electromagnetic materials at the EM detection frequencies. Detection of such resonation causes an alarm to sound if a value token with EM materials are taken past an employee exit gate or are detected by the portable handheld EM detection devices. Such devices are similar to those used by many retail establishments to prevent theft.
The use of the EM materials in gaming chips is limited by the dimensions of the gaming chip. For example, when the EM material is placed beneath the decal, the surface is quite limited. EM material lengths of at least 32-50 mm are desired for reliable detection; however, gaming chips are limited in size to a 40-55 mm diameter, and it is difficult to provide a long decal or label on gaming chips. Typically, the label diameter is limited to 22-24 mm by the gaming chip's disc surface. Such an antenna size is typically insufficient for acceptable EM detection.
One way to address these problems has been to provide a thin metallic foil with hard metal micro-grooves in a metal pad under the decal, one on each side of the gaming chip. However, the metal foil provides a Faraday shield effect at high RF frequencies such as the 13.56 MHz and above signals used for conventional RFID detection. In short, the sensitivity of the RFID antenna to metal shields detunes the RFID antenna rendering it ineffective when such EM foils are provided in the same gaming chip.
As a result, it is typically impossible to provide the EM materials and the RFID detection elements together on the same value token due to interference of the EM and RFID signals. Accordingly, it is desired to design a value token that has the desired weight for handling while permitting the use of RFID microchips and EM detection without unacceptable interference. The invention has been designed to address these and other needs apparent from the following detailed description of the invention.